Electromechanical switches and relays are very commonly used in various applications for automatically selectively switching electrical current on and off. For example, such switches or relays are used in heating, ventilating and air conditioning systems, automobiles and trucks, control circuits, etc. Typically, such switches or relays have a life span which, in large part, depends on the wear of the contacts which occurs as a result of electroerosion. That is, electric sparks occur between the switch contacts which are selectively moved and placed in contact with or apart from one another. These sparks evaporate and/or otherwise deteriorate the contact surfaces thereby eventually decreasing the effective contact surface and also increasing the resistance therebetween such as by accumulation of carbon. This ultimately causes the switch or relay to fail or otherwise become unable to carry or transfer a sufficient current between the conductors.
It is known that electroerosion and carbon buildup on contact surfaces is significantly decreased when the contact action occurs in the absence of air or in a vacuum or if the contact action occurs in the presence of certain arc quenching gases. However, in practice, locating the contacts within a reliable vacuum or arc quenching gas filled enclosure and reliably and inexpensively selectively causing movement of the contacts can be quite difficult. One prior solution, as for example shown in U.S. Pat. No. 3,379,846 to Wood et al., has been to utilize a vacuum tight bellows. There, the contacts are located within a vacuum tight housing or enclosure and are manipulated for switching on and off by mechanical movement which occurs through the bellows. Unfortunately, the bellows of such switches tends to fail over time thereby losing the vacuum or the gases within the switch enclosure or housing. Further, such bellows are typically made of relatively bulky materials making such switches relatively large in size and expensive.
Accordingly, a need exists for an improved electromechanical switch or relay that incorporates a housing or enclosure wherein the switch contacts are located and are isolated from the atmosphere, and wherein the contacts can be manipulated without jeopardizing the integrity of the enclosure or housing and, further, wherein the contacts can be manipulated reliably and the electromechanical switch operates for a substantial number of operations.